1. Technical Field
This document relates to the accurate determination of the rotary position of a rotating device. More specifically, this document relates to an optical position sensor system for determining the angular position of a rotating device and method.
2. Background
In many applications it is important to measure and to control the angular position of a rotary element with high accuracy. For instance, galvanometers require sensors which must detect the angular position of the rotor with extreme accuracy and repeatability, high temperature stability, and high signal to noise ratio. Angular position transducers are used not only to detect the angular position of the rotatable element but also to control and hold the rotatable element in a desired position. For example, a galvanometer can be used to drive a mirror. The mirror can be used to deflect a laser beam which in turn modifies material or objects in a wide variety of applications.
There have been a number of different conventional approaches used in the sensing and detecting of rotary motion. One conventional approach uses one or more light emitting diodes (LEDs) as the light source and reflects the light off a diffuser. This approach has uniform illumination on a detector but has the disadvantage of low output signal levels and poor accuracy. Another conventional approach uses direct illumination from an LED source to illuminate a detector. This approach has good output signal levels but has the disadvantage of requiring the LED source to light blocker and light blocker to detector distances to be very small, which leads to issues with maintaining proper clearance during manufacturing.